Trapping States in CaS and SrS Single Crystals, Films and Powders as Revealed Using the Technique of Transient Thermoluminescence

Trapping centres of doped and undoped CaS and SrS phosphors, in single crystal, thin film and powder forms, have been investigated by the transient thermoluminescence technique. Comparison between the forms are made, and conclusions, regarding the possible sources of the trapping centres, are postulated. The thin films specimens are found to have dramatically different trap spectra, to those observed for single crystal and powder forms. Analysis of the trapping centres, that is the determination of the trap depths, was also carried out, using the aforementioned technique, and the subsequent results compared with those reported in the literature employing the technique of thermoluminescence. The result was a favourable match. Most of the dominant trapping states in these compounds seem related to natural defects and not, directly, to the added dopants.